Antigen: is a a foreign substance or toxin that causes a immune response.
Antibody: it is a blood protein that is produced in response to an antigen.
White blood cell: also called a leukocyte and is a cell that counteracts against antigens.
Specific: If your're talking about the biology definition then it is, of or pertaining to a species.
Pathogen: a virus or bacteria that can cause a disease.
Answer:
a test cross
Explanation:
it determine whether row genes are linked
Explanation:
you just need to know that :
population density = no of ( what is asked) / land area.